The present invention concerns O-ring equipped plug valves for use in high pressure systems.
In existing plug valves a problem exists in keeping their circular, endless seals, termed O-rings, seated in plug defined grooves when controlling fluid flows of several hundred PSI. A pressure differential across an O-ring will cause same to be at least partially displaced from the groove to the extent it is susceptible to being damaged or clipped upon passage across an edge of a port in the valve housing.
In an attempt to prevent such O-ring displacement and resulting damage, various plug configurations have been proposed. U.S. Pat. No. 3,991,975 discloses a plug with an O-ring groove defined by side walls and a bottom wall with the side walls having notches therein to reduce a pressure differential across the O-ring. Reissued patent U.S. Pat. No. Re. 30,224 discloses a plug valve with O-ring receiving grooves having inwardly directed shoulders therealong to retain an O-ring against outward displacement. U.S. Pat. No. 4,262,880 discloses a plug valve wherein port edges in a valve housing are chamfered to reduce O-ring clipping. Further, a channel is shown extending partially about the plug external wall to minimize pressure surges from trapped downstream fluid to avoid O-ring displacement.
Plug valves equipped with O-rings when used for controlling high pressure flows of several hundred PSI have a reduced life by reason of O-ring failure resulting from momentary O-ring displacement whereat it is subject to damaging contact with a port edge of a valve seat.